Technical Field
The present invention relates to austenite heat-resisting cast steel, and particularly relates to austenite heat-resisting cast steel that has an excellent thermal fatigue resistance property.
Background Art
Conventionally austenite heat-resisting cast steel has been used for components of an exhaust system in an automobile, such as an exhaust manifold and a turbine housing. Such components are used in severe environment at high temperatures, and so for excellent thermal fatigue resistance, they are required to have excellent high-temperature strength and such toughness from room temperatures to high temperatures.
From such a point, Patent Document 1, for example, proposes austenite heat-resisting cast steel containing 0.2 to 1.0 mass % of C, 0.05 to 0.6 mass % of C—Nb/8, 2 mass % or lower of Si, 2 mass % or lower of Mn, 8 to 20 mass % of Ni, 15 to 30 mass % of Cr, 0.5 to 6 mass % of Nb, 1 to 6 mass % of W, 0.01 to 0.3 mass % of N, 0.01 to 0.5 mass % of S, Fe as a remainder and unavoidable impurity.
Patent Document 2 proposes austenite heat-resisting cast steel containing 0.05 to 0.65 mass % of C, 0.10 to 3.0 mass % of Si, 0.10 to 11.0 mass % of Mn, 3 to 40 mass % of Ni, 12 to 23 mass % of Cr, N≦10.5 mass %, and the effective Ca amount, which is represented with [Ca mass %]−0.9[O mass %], that is −0.0020 or more.